Enhancement of microbial hydroxylation of 13-ethyl-gon-4-ene-3,17-dione by Metarhizium anisopliae using nano-liposome technique

The introduction of 11 alpha-hydroxy to 13-ethyl-gon-4-ene-3,17-dione (GD) by microbial transformation is a key step in the synthesis of oral contraceptive desogestrel, while low substrate solubility and uptake into cells are tough problems influencing biotransformation efficiency greatly. Nano-liposome technique was used in the hydroxylation of GD by Metarhizium anisopliae. The substrate GD was processed to be GD-loaded nano-liposomes (GNLs) with high stability and encapsulation efficiency, and then applied in microbial hydroxylation by M. anisopliae. The results proved that the yield of the main product 11 alpha-hydroxy-13-ethyl-gon-4-ene-3,17-dione (HGD) tripled compared to regular solvent dimethylformamide dispersion method at 2 g/l of substrate feeding concentration, and the HGD conversion rate showed no obvious reduction when the substrate feeding concentration increased from 2 to 6 g/l, which indicated the improvement of GNL addition method on biotransformation. Furthermore, the main byproduct changed from 6 beta-hydroxy derivative of GD (with similar polarity to HGD) to 6 beta,11 alpha-dihydroxy derivative, which benefits the following purification of HGD from fermentation broth. These advantages suggest a great potential for the application of nano-liposome technique in microbial steroid transformation.